Top Democrats warned Republicans Monday not to stymie investigations into contacts between President Donald Trump's campaign and Russia, as the White House sought to quell a media storm over the allegations.

The warnings came after Trump's staff sought to enlist the FBI, reportedly the CIA and two Republicans who head committees leading the Russia investigations, to knock down media reports on the alleged links.

The Democrats said that effort threatened to politically taint probes by both the security agencies and congressional committees into Russian interference in last year's presidential election and alleged communications between Trump team officials and Russian intelligence.

"This is not the way to conduct a fair, impartial investigation that goes where the facts lead," said Senator Chuck Schumer, leader of the Democrats in the Senate. "It certainly gives the appearance if not the reality of lack of impartiality."

- Political interference -
Senator Mark Warner, the senior Democrat on the Senate Intelligence Committee, said its investigation into the Russia issue needs to remain bipartisan.

"It shouldn't have political interference; it can't go where the White House wants it to go," he told CNN. "By trying to bring in others to interfere with investigations, then they are going to color any results that come out."

The Trump administration is battling accusations that onetime campaign chair Paul Manafort and others had communications with Russian officials before the election at the same time that Moscow allegedly conducted a campaign of hacking and information releases aimed at harming Trump's rival in the election, Hillary Clinton.

The New York Times reported, citing intelligence sources, that the communications were with Russian intelligence officials.

The White House admitted last week asking the Federal Bureau of Investigation to help it combat what it labeled the "false" New York Times report, by making information from its own investigation public.

"This started with the FBI bringing it to us, bringing it to our attention, saying the story in the Times was not accurate," White House spokesman Sean Spicer said Monday.

"All we said is: 'That's great, could you tell other reporters the same thing you are telling us?'"

After the FBI declined to take a public stance, the White House sought the help of Republican Senator Richard Burr, who chairs the Senate Intelligence Committee, and Devin Nunes, Republican chair of the House Intelligence Committee that is also conducting a probe, to shoot down the report.

"All we sought to do was get an accurate report out," said Spicer, fending off comments that his actions were inappropriate.

"So, you know, respectfully, I think it's interesting that I'm being asked what's appropriate when what we are doing is actually urging reporters to engage with subject matter experts who can corroborate whether or not something is accurate or not."

- 'No evidence' says Republican -
But Democrats reacted sharply Monday as Nunes, before his committee held any hearings on the alleged Russia contacts, said he did not see any evidence to investigate.

"Here at the committee, we still don't have any evidence of them talking to Russians," Nunes told journalists.

"And what I've been told by many folks is that there is nothing there."

Nunes was quickly berated by his Democratic vice-chair Adam Schiff, who said the committee has not even received any evidence or testimony, so that it was impossible to make such a determination.

"We haven't obtained any of the evidence yet. So it's premature for us to be saying that we have reached any conclusion about the issue of collusion," he said.

"You don't begin by stating what you believe to be the conclusion."

Some Democrats have called for a bipartisan committee or an independent prosecutor to be named to probe the Russia issue.

On Friday, Republican Congressman Darrell Issa became the first member of his party to endorse the idea of an independent investigation, possibly under a special prosecutor.